1. Field of the Invention
This invention relates to switching devices and particularly circuit breakers in which electrical contacts and an operating mechanism therefor are enclosed by a removable cover in an insulated housing with an operating handle extending outward through and movable in a slot in the cover. More specifically, the invention is directed to an interlock associated with the handle which prevents removal of the cover if the electrical contacts are not open.
2. Background Information
Electrical switching devices, such as in particular, circuit breakers, typically have one or more sets of electrical contacts and an operating mechanism for the contacts inserted through an opening into an insulated housing. The opening is closed by a cover so that the electrical contacts and operating mechanism are completely enclosed. Typically, a handle connected to the operating mechanism extends outward through a slot in the cover. This handle, through which the contacts can be manually operated, also provides a visual indication of the position of the electrical contacts and of the operating mechanism. Circuit breakers include a trip unit which actuates the operating mechanism to open the contacts in response to abnormal current flow through the device. This tripping of the circuit breaker moves the handle to a trip position which provides a visual indication of the trip.
Normally, the circuit breaker is connected so that only the stationary contacts are energized when the circuit breaker is tripped or off. However, when the contacts are closed there is a completed circuit through the contacts and portions of the trip unit. Removal of the cover with the contacts closed exposes these energized components. While the stationary contacts remain energized when the device is tripped or off, typically they are located in the deepest recesses of the housing and are not as likely to be contacted.
In some applications, low cost circuit breakers having the basic configuration described above are utilized as switches for particular loads, such as for instance, motors. While such devices may provide protection against severe overloads or faults, their primary function is as a switch. Removal of the cover from such a switch when the contacts are closed, also exposes energized components.
There is a need therefore for a simple, economical interlock for the above described switching devices which prevents removal of the cover, and therefore exposure of energized components, when the electrical contacts are closed.
There is a further need for such an interlock which can be easily applied to existing switching devices.